Voltage detectors commonly used to detect the presence of high voltages use microcontrollers to automatically control parts of the devices such as the voltage input and the display. The display of a voltage detector may be intermittently refreshed in order to provide a visual indication of input voltages detected by the detector in real time. The microcontroller may be used to control the refreshing of the display and hence the accuracy of the voltage values displayed.
Microcontrollers may also contain a watchdog timer that triggers a system reset or other corrective action if the microcontroller, due to some fault condition, neglects to regularly service the watchdog. The intention is to bring the system back from the unresponsive state into normal operation. The most common use of watchdog timers is in embedded systems, where the watchdog timer is often a built-in unit of a microcontroller. A watchdog timer may also be external to the microcontroller. Watchdog timers may also trigger fail-safe control systems to move into a safety state, such as turning off high-voltage electrical outputs, and other potentially dangerous subsystems until the fault is cleared.
A disadvantage of such a voltage detector is that if the microcontroller malfunctions, the value of voltage displayed may not accurately represent the actual detected voltage. For example, the voltage detected may be much higher than the value displayed thereby exposing the user to extreme risk of injury.